alleryThe excess pressure inside a spherical liquid drop of radius R and surface tension T is:
AT / R
BT / (2 R)
C4 T / R
D2 T / R
Answer & Solution
Correct answer: D. 2 T / R
1. For a drop (single surface), Laplace's relation gives ΔP = 2 T / R.
2. For a soap bubble (TWO surfaces — inner + outer), ΔP = 4 T / R.
3. The smaller the drop, the larger the excess pressure — why fine droplets evaporate first.
_Source: syllabus Physics Ch 9 §9.8 Drops, Bubbles, Capillary Action_
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